It has long been assumed that as people develop, the nerve patterns used to control motion during infancy become suppressed, and are replaced instead by entirely new patterns of neuronal activity that allow them to move with greater purpose and precision.
Now, new research shows that this may not be the case. By examining the activity of motor neurons in newborns, toddlers, preschoolers and adults, a team of Italian researchers has revealed that basic neural patterns required for walking are, in fact, retained through development. What's more, their results suggest that human babies actually learn to walk using the same network of spinal nerve cells as rats, cats, monkeys and birds. And you thought humans were so special.
Hang on, though — let's take a step back for a moment. How do you even go about measuring the neural patterns required for walking in a newborn baby… if it can't even walk?
I'm so glad you asked.
Because it turns out even a newborn pretty much knows how to walk instinctively, provided it's given proper support. The video featured here shows a three-day-old child from the experiment plodding along with the assistance of a researcher.
See the white mesh on the baby's legs? Those are electromyographs. They're used to measure patterns of activity and communication between the baby's motor neurons. When the researchers examined the activity they found that the newborns' spinal cord neurons are activated in two distinct phases. The first directs the legs to bend and extend; the second commands the baby's legs to alternate — left, right, left, right — in order to move forward.
By the time these babies are able to walk on their own, however, their patterns of motor activity look much different. Interestingly, the original two phases of spinal cord activation are still there, but now two new neural patterns emerge, which the researchers believe are responsible for more subtle motions relating to balance, weight shifting and step timing.
But here's where things get really interesting. When the researchers compared the babies' motor commands with those observed in previous studies of various animals, they found their neural circuitry to be almost identical. The researchers describe their findings in the latest issue of Science:
We found that the two basic patterns of stepping neonates are retained through development, augmented by two new patterns first revealed in toddlers. Markedly similar patterns were observed also in the rat, cat, macaque, and guineafowl, consistent with the hypothesis that, despite substantial phylogenetic distances and morphological differences, locomotion in several animal species is built starting from common primitives, perhaps related to a common ancestral neural network.
Translation? According to neurophysioloist Francesco Lacquaniti, who led the study: "During evolutionary history, nature didn't scrap the old hardware. Instead it was modified and tuned to adapt to our needs."
Oh, nature. Sometimes you can be so resourceful.